Re: Strange 8255 behavior

From: Michał Pleban <*lists_at_michau.name*> Date: Sun, 10 Jun 2018 15:47:29 +0200 Message-ID: <5B1D2BF1.1070702@michau.name> · lists_at_michau.name

Gerrit Heitsch wrote:

> Might not be possible since the 6525 has NMOS output drivers which allow
> you to do things that you can't do with CMOS output drivers. Namely
> having 2 outputs (one LOW, one HIGH) directly connected.

The only role the 6525 has on the board is to connect to the 6526 on the
other side to pass some signals.

So what we thought to do was rather implement *both* the 6525 and 6526
in the CPLD, or more precisely, only these parts which are necessary for
this particular interface. Then the CPLD would be directly connected to
the 8088 bus on one side and 6509 bus on the other side. I don't know
about 8088, but I have already connected a CPLD to the 6509 before and
it worked like a charm.

Regards,
Michau.